According to one example a blade fatigue test to a wind turbine blade or a wind turbine rotor blade may comprise the following steps:                the blade is bolted and/or clamped to a test rig and visually inspected,        strain gauges are applied to the blade skin and wiring is done,        an eccentric mass exciter and dead loads are mounted onto the blade to obtain the required cross sectional bending moments, and also to obtain R-ratios close to the required,        a static calibration test is performed to obtain strain- and stiffness information for the blade in the cross sections equipped with strain gauges; the load level in terms of the bending moment range at the root interface is determined,        the blade is subject to the required number of load cycles. A frequency converter powers the electric motor exciter mounted on the blade. This forces the blade with all additional masses to oscillate in a flapwise direction at a frequency close to the natural frequency. A control system ensures that the root bending moment range is kept at a constant level during the test,        at a specified number of load cycles a scan of all strain gauges is performed automatically, to record the strain range at every gauge position,        
Static calibration tests are performed at regular intervals of, for example, one million cycles to monitor structural changes of the blade.
A common concern related the above described tests is the amount of power consumed during testing. Hence, there is a desire for reducing the energy consumption at wind turbine blade fatigue testing.